Types of Radiation Therapy
High Dose Rate Brachytherapy (HDR)
High Dose Rate Brachytherapy (HDR) allows a high dose of radiation to be delivered directly to the tumor or tumor bed (area from which the tumor has been removed). This is done by using a radioactive material (referred to as a source, seeds, or implant) sealed in a thin wire, catheter (tube) and placed directly into the affected tissue. The types of radiation used for HDR include cesium, iridium, iodine, phosphorus, and palladium. Areas that may be treated with HDR include the head and neck, breast, uterus, thyroid, cervix, and prostate. This internal source of radiation may be used by itself or with external radiation therapy. The size and location of the tumor will determine the type of HDR therapy given.
Some of the more common methods of delivery are:
- Interstitial (placing the implant or source into the tumor by using catheters, seeds, or capsules)
- Intracavitary (placing special applicators inside a body cavity such as the uterus)
- Intraluminal (placing special applicator into a passageway such as the bronchus)
- Surface Brachytherapy (placing sealed source in or against the tumor)
- Unsealed internal (injecting radioactive substance into the bloodstream or body cavity such as samarium)
- High dose sources of radiation may be left in place for a matter of minutes, where as low dose sources may be left in place for several days. Once the radioactive source is removed, you are not "radioactive". Interstitial radiation may be left in place permanently through the use of seeds. It may be necessary for you to take special precautions for a few days after the implant is placed.
Samarium is a radioactive liquid that is used to provide relief from the severe and debilitating pain of bone metastases (spread of cancer to the bones). Pain control can help the patient stay involved in not only cancer treatment, but also other areas of life. A single intravenous (into a vein) injection of samarium is given on an out-patient bases. The radiation in samarium is delivered to the cancer cells while very little radiation is given to healthy cells. Pain relief may start as early as one week after injection and may continue improving for four months. Many patients are able to reduce or completely eliminate the use of pain medications. Most patients have no side effects from samarium therapy. A slight increase in bone pain may be noticed within the first few days after injection. This is usually relieved by over-the-counter pain medications. Occasionally a temporary decrease in blood counts may be seen in the first eight weeks.
Prostate Brachytherapy is internal radiation to the prostate gland. The radiation is placed into the prostate during a minor outpatient surgical procedure performed by an urologist (physician specializing in problems of the urinary tract and male reproductive organs) and a radiation oncologist (physician specializing in the use of radiation in cancer treatment). The source of radiation is called a "seed". This seed is approximately the size of a grain of rice and too small to cause discomfort. Approximately 90 seeds are placed into the prostate gland using ultrasound guidance. The patient is anesthetized (put to asleep) and most patients report that they experience no discomfort during the procedure.
There are several advantages to prostate brachytherapy:
- Effective in treating localized prostate cancer
- Low risk of major complications
- Low risk of impotence (sexual dysfunction)
- Low risk of incontinence (sudden unintentional release of urine)
- Minor outpatient surgery procedure
- Very short time until the patient can return to regular activities
- Ultrasound Guided Prostate Radiation Therapy
- Ultrasound guided prostate radiation therapy uses ultrasound waves to pinpoint the location of the prostate gland daily within the body thus avoiding high doses of radiation to healthy surrounding tissues. Avoiding the healthy tissues reduce the chance of undesirable side effects from radiation to the bladder and rectum such as diarrhea and painful or frequent urination. Standard radiation therapy typically includes an extra margin of healthy tissue outside of the prostate gland in the radiation beam to allow for the shifting of internal organs. The radiation therapist uses marks located on the patient's skin to position the prostate gland in the field of the radiation beam. The marks on the skin may be slightly different than the internal location of the organs on a day to day bases due to several factors (example: bladder full verses empty, gas, constipation, bloating). With daily ultrasound scanning, the radiation therapist receives computer guidance to position the patient on the treatment couch. Because the location of the prostate gland is no longer uncertain, the margin around it can be reduced. This reduction in treatment field size helps to minimize the amount of radiation received by normal healthy tissue.
Intensity Modulated Radiation Therapy (Imrt)
Intensity Modulated Radiation Therapy (IMRT) allows radiation beams of various strengths and shape to be delivered from several angles. IMRT uses inverse treatment planning to determine the best treatment plan to achieve these goals. Multileaf collimation (MLC) makes this possible by using the computer controlled tungsten leaves located inside the linear accelerator (radiation treatment machine) to form the radiation fields. This allows a higher dose of radiation to be delivered to the area of the body needing radiation treatment while minimizing radiation to the healthy surrounding tissue.
Three Dimensional Conformal Radiation Therapy
Three Dimensional Conformal Radiation Therapy (3DCRT) involves the use of computer simulation of the tumor and surrounding areas allowing the radiation beam to be shaped exactly to the tumor, sparing surrounding normal tissues. A special Computed Axial Tomography Scan (CAT scan) of the tumor site is acquired and the images are sent to our planning computer. The physics team at our facility develops a radiation plan from the CAT scan. The Elekta Linear Accelerator used at our facility uses Multi-Leaf Collimation to form the radiation fields developed by our physics team. Each leaf is made of tungsten and is located inside the linear accelerator. The leaves can be moved in or out of the radiation beam as prescribed. This allows the radiation beam to be shaped to match the shape and size of your tumor. This means less tissue damage to your body and fewer side effects from the treatment.
Mammosite® Radiation Therapy
Mammosite® radiation therapy is a treatment option for women with early stage breast cancer allowing them to avoid mastectomy and external beam radiation therapy. Some cancer cells may be missed during lumpectomy surgery. Mammosite® allows a high dose of radiation to be given to the area where it is needed most. The treatment procedure is done through a small soft balloon attached to a thin catheter (tube) placed by the surgeon inside the space where the cancer was removed. This placement may be done during the lumpectomy surgery or up to ten weeks afterwards. A portion of the catheter will remain on the outside of the breast until treatment is completed. This will be taped to the breast and afterwards, the patient can go home. The catheter will typically remain in the breast for seven to ten days. The actual radiation treatment will last no more than five days. Radiation therapy will consist of a tiny radioactive seed being placed into the Mammosite® catheter twice a day. Each treatment will last approximately ten minutes. Once the prescribed amount of radiation has been delivered the radioactive seed will be removed each time. Since the radiation is located in the seed, the patient will not be radioactive after each treatment session is completed. Treatment with Mammosite® will be completed in one to five days. After the final treatment the balloon will be deflated and the catheter easily removed.